Mobile street sweepers are commonly employed by municipalities to remove debris and dust from streets and other flat surfaces such as parking lots, runways and the like. Such street sweepers typically include a vehicle chassis and one or more rotating brooms mounted to the chassis for dislodging the debris from the surface to be swept. The debris is moved from the rotating brooms to a hopper for collection. Moving the debris may be accomplished by a powerful blower communicating with the hopper and drawing debris into the hopper or by a mechanical means such as a conveyor assembly. To empty the hopper when desired, the street sweeper can be adapted to lift and tilt the hopper with respect to the chassis.
To prevent debris collected in the hopper from escaping back to the environment, the hopper is formed as an enclosed structure that defines an internal volume. Except during emptying, access to the internal volume is limited to the deposit of debris from the rotating brooms. As such, the conditions of the internal volume are maintained in such a manner as to reduce or eliminate shifting air currents that can disrupt the collected debris. In some street sweeper systems, especially those utilizing mechanical means to convey debris to the hopper, a dust control system can also be provided that eliminates dust by exhausting air from the internal volume through a filter.
Since the rotating brooms are directed toward and proximate the street surface, debris removal by the street sweeper can only occur from the street surface. This hinders the removal of debris from difficult to reach areas, such as sidewalks, bus stop shelters, and around light posts. Additionally, in some instances, the size and nature of the debris may be such that collection via the rotating brooms could damage the street sweeper.